Word-of-mouth is the only really trustworthy form of advertisement, and the web extends the reach of word-of-mouth across continents.
I don't think letterpress printers are in competition with each other. We each have our own distinct styles. The more the world knows about printers and printing, the more of the world we printers will meet.
We are a tight-knit community. We frequently call each other up to talk shop, kvetch, or help each other out, all in the long tradition of San Francisco Bay Area fine printing.
Plus, what's the web without links?